Additives for inhibiting the formation of gas hydrates

ABSTRACT

The invention relates to an additive, the use thereof and a method for inhibiting the seeding, growth and/or agglomeration of gas hydrates, whereby an effective amount of an inhibitor is added to a multi-phase mixture, comprising water, gas and, optionally, condensate, which tends to form hydrates or a drilling fluid which tends to form gas hydrates. Said inhibitor contains doubly alkoxylated quaternary ammonium compounds, whereby compounds of formula (1), where R 1 , R 2  independently=groups of formula —(B)—(O—A) n —O—CO—R 5  (2), or —(A—O) n —(C)—CO—O—R 5  (3), R 3 =C 1  to C 30  alkyl or C 2  to C 30  alkenyl, R 4 =an organic group with 1 to 100 carbon atoms, optionally containing heteroatoms, R 5 =C 1  to C 30  alkyl or C 2  to C 30  alkenyl, n=1 to 20; A=a C 2  to C 4  alkylene group, B=a C 1  to C 10  alkylene group, C=a C 1  to C 6  alkylene group and X=an anion, are used as gas hydrate inhibitors.

[0001] The present invention relates to an additive, to its use and to aprocess for inhibiting nucleation, growth and/or agglomeration of gashydrates by adding an effective amount of an inhibitor to a multiphasicmixture which tends to hydrate formation and consists of water, gas andoptionally condensate, or to a drilling fluid which tends to gas hydrateformation, said inhibitor comprising dialkoxylated quaternary ammoniumcompounds.

[0002] Gas hydrates are crystalline inclusion compounds of gas moleculesin water which form under certain temperature and pressure conditions(low temperature and high pressure). The water molecules form cagestructures around the appropriate gas molecules. The lattice structureformed from the water molecules is thermodynamically unstable and isonly stabilized by the incorporation of guest molecules. Depending onpressure and gas composition, these icelike compounds can exist even toabove the freezing point of water (up to above 25° C.).

[0003] In the crude oil and natural gas industry, great significanceattaches in particular to the gas hydrates which form from water and thenatural gas constituents methane, ethane, propane, isobutane, n-butane,nitrogen, carbon dioxide and hydrogen sulfide. Especially in modernnatural gas extraction, the existence of these gas hydrates constitutesa great problem, especially when wet gas or multiphasic mixtures ofwater, gas and alkane mixtures are subjected to low temperatures underhigh pressure. As a consequence of their insolubility and crystallinestructure, the formation of gas hydrates leads here to the blockage of awide variety of extraction equipment such as pipelines, valves orproduction equipment in which wet gas or multiphasic mixtures aretransported over relatively long distances at relatively lowtemperatures, as occurs especially in colder regions of the earth or onthe seabed.

[0004] In addition, gas hydrate formation can also lead to problems inthe course of the drilling operation to develop new gas or crude oildeposits at the appropriate pressure and temperature conditions by theformation of gas hydrates in the drilling fluids.

[0005] In order to prevent such problems, gas hydrate formation in gaspipelines, in the course of transport of multiphasic mixtures or indrilling fluids, can be suppressed by using relatively large amounts(more than 10% by weight, based on the weight of the aqueous phase) oflower alcohols such as methanol, glycol or diethylene glycol. Theaddition of these additives has the effect that the thermodynamic limitof gas hydrate formation is shifted to lower temperatures and higherpressures (thermodynamic inhibition). However, the addition of thesethermodynamic inhibitors causes serious safety problems (flashpoint andtoxicity of the alcohols), logistical problems (large storage tanks,recycling of these solvents) and accordingly high costs, especially inoffshore extraction.

[0006] Attempts are therefore being made today to replace thermodynamicinhibitors by adding additives in amounts of <2% in temperature. andpressure ranges in which gas hydrates can form. These additives eitherdelay gas hydrate formation (kinetic inhibitors) or keep the gas hydrateagglomerates small and therefore pumpable, so that they can betransported through the pipeline (agglomerate inhibitors oranti-agglomerates). The inhibitors used either prevent nucleation and/orthe growth of the gas hydrate particles, or modify the hydrate growth insuch a way that relatively small hydrate particles result.

[0007] The gas hydrate inhibitors which have been described in thepatent literature, in addition to the known thermodynamic inhibitors,are a multitude of monomeric and also polymeric substance classes whichare kinetic inhibitors or agglomerate inhibitors. Of particularsignificance in this context are polymers having a carbon backbone whichcontain both cyclic (pyrrolidone or caprolactam radicals) and acyclicamide structures in the side groups.

[0008] EP-B-0 736 130 discloses a process for inhibiting gas hydrateswhich entails feeding a substance of the formula

[0009] where X=S, N—R₄ or P—R₄, R₁, R₂ and R₃=alkyl having at least 4carbon atoms, R₄=H or an organic radical, and Y=anion.

[0010] This therefore includes compounds of the formula

[0011] where R₄ may be any desired radical, but the R₁ to R₃ radicalshave to be alkyl radicals having at least 4 carbon atoms. Nodialkoxylation is disclosed.

[0012] EP-B-0 824 631 discloses a process for inhibiting gas hydrateswhich entails feeding a substance of the formula

[0013] where R₁, R₂=linear/branched alkyl radicals having 4 or 5 carbonatoms, R₃, R₄=organic radicals having at least 8 carbon atoms andA=nitrogen or phosphorus. Y⁻ is an anion. Two of the R₁ to R₄ radicalshave to be linear or branched alkyl radicals having 4 or 5 carbon atoms,and no dialkoxylation is disclosed.

[0014] U.S. Pat. No. 5,648,575 discloses a process for inhibiting gashydrates. The process comprises the use of a compound of the formula

[0015] where R¹, R² are linear or branched alkyl groups having at least4 carbon atoms, R³ is an organic radical having at least 4 atoms, X issulfur, NR⁴ or PR⁴, R⁴ is hydrogen or an organic radical, and Y is ananion. The document discloses only those compounds which have at leasttwo alkyl radicals having at least 4 carbon atoms, and no dialkoxylationis disclosed.

[0016] U.S. Pat. No. 6,025,302 discloses polyetheramine ammoniumcompounds as gas hydrate inhibitors whose ammonium nitrogen atom, inaddition to the polyetheramine chain, bears 3 alkyl substituents.

[0017] U.S. Pat. No. 5,523,433 discloses compounds of the formula

[0018] where R^(a) and R^(b) may each be C₁₂- to C₂₂-alkyl radicals andR¹ and R² may each be C₁- to C₄-alkyl radicals. The document disclosesthe suitability of such compounds as a constituent of fabric softeners.

[0019] WO-99/13197 discloses ammonium compounds as gas hydrateinhibitors, which may also be alkoxylated, but not the advantages ofdi-N-alkoxylation.

[0020] WO-01/09082 discloses quaternary amides as gas hydrate inhibitorswhich, however, bear no alkoxy groups.

[0021] WO-00/078 706 discloses quaternary ammonium compounds as gashydrate inhibitors which, however, bear no carbonyl radicals.

[0022] The additives described have only limited effectiveness askinetic gas hydrate inhibitors and/or antiagglomerates, have to be usedwith coadditives, or are not obtainable in a sufficient amount or onlyat high prices.

[0023] In order to be able to use gas hydrate inhibitors even atstronger supercooling than currently possible, i.e. further within thehydrate region, a further increase in activity is required in comparisonto the prior art hydrate inhibitors. In addition, improved products aredesired with regard to their biodegradability, anticorrosive propertiesand toxicity.

[0024] It is thus an object of the present invention to find improvedadditives which not only slow the formation of gas hydrates (kineticinhibitors) but also keep gas hydrate agglomerates small and pumpable(antiagglomerates), in order to thus ensure a broad spectrum ofapplication with a high action potential. In addition, it should bepossible to replace the thermodynamic inhibitors used currently(methanol and glycols) which cause considerable safety problems andlogistical problems.

[0025] Prior art gas hydrate inhibitors are commonly coadditized withcorrosion inhibitors, in order to prevent corrosion of the transport andextraction equipment. As a consequence of the frequent lack of immediatecompatibility of gas hydrate inhibitor and corrosion protector in thecourse of formulation, there is additional work for the user. It wouldbe a significant advantage over the prior art if coadditization withcorrosion inhibitors were no longer obligatory.

[0026] It has now been found that, surprisingly, di-N-alkoxylated andcarbonylated ammonium salts have excellent action as gas hydrateinhibitors. Their corrosion-inhibiting action is so good that noadditization with further corrosion inhibitors is required.

[0027] The present invention thus provides the use of compounds of theformula 1

[0028] where

[0029] R¹, R² are each independently radicals of the formulae

—(B)—(O—A)_(n)—O—CO—R⁵  (2)

[0030] or

—(A—O)_(n)—(C)—CO—O—R⁵  (3)

[0031] R³ is C₁- to C₃₀-alkyl or C₂- to C₃₀-alkenyl,

[0032] R⁴ is an organic radical which optionally contains heteroatomsand has from 1 to 100 carbon atoms,

[0033] R⁵ is C₁- to C₃₀-alkyl or C₂- to C₃₀-alkenyl,

[0034] n is a number from 1 to 20,

[0035] A is a C₂- to C₄-alkylene group,

[0036] B is a C₁- to C₁₀-alkylene group,

[0037] C is a C₁- to C₆-alkylene group and

[0038] X is an anion

[0039] as gas hydrate inhibitors.

[0040] The invention further provides a process for inhibiting gashydrates by adding at least one compound of the formula 1 to a systemwhich tends to form gas hydrates and is composed of water andhydrocarbons.

[0041] The invention further provides the compounds of the formula (1),although excluding those compounds in which R⁴ contains no heteroatomand R¹ and R² are at the same time as defined in formula (2).

[0042] In the context of this invention, hydrocarbons are volatilehydrocarbons, for example methane, ethane, propane, butane. For thepurposes of this invention, these also include the further gaseousconstituents of crude oil/natural gas, for instance hydrogen sulfide andcarbon dioxide.

[0043] A may be straight-chain or branched and is preferably an ethyleneor propylene group, in particular an ethylene group. The alkoxy groupsdenoted by (A—O)_(n) may also be mixed alkoxy groups.

[0044] B may be straight-chain or branched and is preferably a C₂- toC₄-alkylene group, in particular an ethylene or propylene group.

[0045] C may be straight-chain or branched and is preferably a C₂- toC₄-alkylene group, in particular a methylene or ethylene group.

[0046] n is preferably a number in the range from 2 to 6.

[0047] R⁵ is preferably an alkyl or alkenyl group having from 2 to 24carbon atoms, in particular from 4 to 12 carbon atoms.

[0048] R³ is preferably an alkyl or alkenyl group having from 2 to 12carbon atoms, in particular those groups having from 4 to 8 carbon atomsand especially butyl groups.

[0049] R⁴ may be any desired organic radical which contains from 1 to100 carbon atoms and which may contain heteroatoms. When R⁴ containsheteroatoms, they are preferably nitrogen or oxygen atoms or both,preferably both. The nitrogen atoms may be present in quaternized form.

[0050] In a further preferred embodiment, R⁴ includes from 1 to 20alkoxy groups which are derived from C₂- to C₄-alkylene oxide, inparticular from ethylene oxide and/or propylene oxide. In particular, R⁴may be a radical of the formula (2) or (3).

[0051] In a particularly preferred embodiment, R⁴ is a radical of theformula (4)

[0052] where the bond to the nitrogen atom in formula 1 is via the freevalence of the (CH₂)_(k) group. In formula (4), R⁶ is a radical of theformulae

—(B)—(O—A)_(n)—O—CO—R⁵  (2)

[0053] or

—(A—O)_(n)—(C)—CO—O—R⁵  (3)

[0054] or C₁- to C₃₀-alkyl or C₂- to C₃₀-alkenyl, each with the areas ofpreference specified above for A, B, n, R³ and R⁵. k is 2 or 3, and R¹and R³ are each as defined above.

[0055] Suitable counterions X are all ions which do not impair thesolubility of the compounds of the formula (1) in the organic-aqueousmixed phases which tend to gas hydrate formation. Such counterions are,for example, methyl-sulfate ions (methosulfate) or halide ions.

[0056] Particularly preferred compounds (illustrated withoutcounterions) correspond to the formulae (5) to (8)

[0057] The inventive compounds can be used alone or in combination withother known gas hydrate inhibitors. In general, enough of the inventivegas hydrate inhibitor will be added to the system which tends to hydrateformation to obtain sufficient inhibition under the given pressure andtemperature conditions. The inventive gas hydrate inhibitors are usedgenerally in amounts between 0.01 and 5% by weight (based on the weightof the aqueous phase), corresponding to 100-50 000 ppm, preferably from0.02 to 1% by weight. When the inventive gas hydrate inhibitors are usedin a mixture with other gas hydrate inhibitors, the concentration of themixture is from 0.01 to 2 or from 0.02 to 1% by weight in the aqueousphase.

[0058] For use as gas hydrate inhibitors, the inventive compounds arepreferably dissolved in alcoholic solvents such as aqueous monoalcohols,for example methanol, ethanol, propanol, butanol, and also oxyethylatedmonoalcohols such as butylglycol, isobutylglycol, butyldiglycol andpolyglycols. In addition, it has been found that, surprisingly, theinventive compounds of the formula (1) and (4) function as corrosioninhibitors. Additional additization with corrosion inhibitors istherefore in some cases no longer necessary, so that complicatedformulation taking into account the compatibility of gas hydrateinhibitor and corrosion protection component for the user is no longernecessary.

[0059] The inventive compounds can be prepared by reacting alkoxylatedalkylamines or alkylaminoalkylenamines with monochlorocarboxylic acidsto give the corresponding ethercarboxylic acids and subsequentlyesterifying them with alkanols. Alternatively, the bisalkoxylatedmonoalkylamines or alkylaminoalkylenamines can be reacted directly withcarboxylic acids and their derivatives such as anhydrides, carbonylchlorides or their esters to give the inventive esters. This is followedby quaternization with suitable alkylating agents.

[0060] The preparation of alkoxylated alkylamines andalkylaminoalkylenamines has been described in the prior art.

[0061] The alkoxylated alkylamines used are based on alkylamines havingC₁- to C₃₀-alkyl radicals or C₂- to C₃₀-alkenyl radicals, preferably C₃-to C₈-alkylamines. Suitable alkylamines are, for example, n-butylamine,isobutylamine, pentylamine, hexylamine, octylamine, cyclopentylamine,cyclohexylamine.

[0062] The alkoxylated alkylaminoalkylenamines used are based onaminoalkylenamines having C₁- to C₃₀-alkyl radicals or C₂- toC₃₀-alkenyl radicals and k=2 or 3. Suitable aminoalkylenamines are, forexample, fatty alkyl propylenediamines such as tallow fatpropylenediamine, stearylpropylenediamine, oleylpropylenediamine,laurylpropylenediamine, dodecylpropylenediamine andoctylpropylenediamine.

[0063] The alkylamines or alkylaminoalkylenamines are generally reactedtogether with ethylene oxide, propylene oxide, butylene oxide ormixtures of different such alkylene oxides, although preference is givento ethylene oxide or mixtures of ethylene oxide and propylene oxide.Based on alkylamine or alkylaminoalkylenamines, 1-40 mol of alkyleneoxide are charged, preferably 1-12 mol.

[0064] The alkoxylation is effected without solvent, but can also becarried out in solution. Suitable solvents for the alkoxylation areinert ethers such as dioxane, tetrahydrofuran, glyme, diglyme and MPEGs.

[0065] In general, the alkoxylation in the first reaction step iscarried out uncatalyzed up to >95% by weight of tertiary nitrogen.Higher alkoxylation is effected after addition of basic compounds ascatalysts. Useful basic compounds are alkaline earth metal/alkali metalhydroxides or alkoxides (sodium methoxide, sodium ethoxide, potassiumtert-butoxide), but preference is given to alkali metal hydroxides,particularly sodium hydroxide or potassium hydroxide.

[0066] For the preparation of the inventive compounds, theamine-oxyethylate mixtures are reacted in a subsequent reaction stepwith a chlorocarboxylic acid derivative and a base, preferably drychloroacetic acid sodium salt and sodium hydroxide. This can be effectedby reacting the oxyethylate mixture with from 100 to 150 mol % of sodiumchloroacetate at from 30 to 100° C. and, simultaneously or insuccession, admixing with solid sodium hydroxide or potassium hydroxide,so that the sum of the base already present in the oxyethylate mixtureand the additionally added amount of base corresponds to the amount ofsodium chloroacetate. The amount of base which has already beencontained from the reaction with the alkylene oxide can thus be useddirectly for the subsequent Williamson synthesis and does not have to bewashed out, as in the synthesis of a standard oxyethylate.

[0067] Following the alkylation reaction, the alkoxylatedamine-ethercarboxylic acid alkali metal salts are converted to the freeethercarboxylic acid. To this end, they are acidified to pH<3 usingstrong mineral acid (hydrochloric acid, sulfuric acid) and theethercarboxylic acid is removed hot as the upper phase by phaseseparation above its cloud point.

[0068] The alkoxylated amine-ether carboxylic acids are subsequentlyesterified generally by direct reaction of the free acid withcorresponding alcohols at temperatures of 100-200° C. at which the waterof reaction is removed distillatively. The esterification can beaccelerated by adding suitable acidic catalysts having a pK_(a) of lessthan 5 or by separating out the water of reaction with suitablesolvents. Suitable catalysts are, for example, sulfonic acid andalkylstannic acids.

[0069] For the esterification of the alkoxylated amine-ether carboxylicacids, alcohols having C₄- to C₃₀-alkyl radicals or C₄- to C₃₀-alkenylradicals are used, preferably fatty alcohols. Suitable alcohols are, forexample, 2-ethylhexanol, octanol, decanol, lauryl alcohol, palmitylalcohol, stearyl alcohol and oleyl alcohol.

[0070] The inventive compounds can also be prepared by esterifying theamine-oxyethylate mixtures with carboxylic acids and their derivativessuch as carbonyl chlorides, carboxylic anhydrides and carboxylic esters.The esterification with free carboxylic acids is effected attemperatures of 100-200° C., at which the water of reaction is removeddistillatively. The esterification can be accelerated by adding suitableacidic catalysts having a pK_(a) of less than 5 or by separating out thewater of reaction with suitable solvents. Suitable carboxylic acids areacetic acid, propionic acid, caproic acid, caprylic acid,2-ethylhexanoic acid and fatty acids, or their anhydrides, methyl estersand chlorides.

[0071] The inventive compounds are then prepared by quaternizing thetertiary nitrogen atoms with a suitable alkylating agent at from 50 to150° C. Suitable alkylating agents are alkyl halides and alkyl sulfates,preferably methylene chloride, butyl bromide and dimethyl sulfate.

EXAMPLES

[0072] a) General Method for the Preparation of AlkoxylatedAmine-ethercarboxylic Acids

[0073] A stirred apparatus was initially charged with 2 mol of theappropriate alkoxylated amine or 1 mol of the appropriate alkoxylateddiamine (according to OH number) with nitrogen purging and heated to 40°C. 650 g (4.8 mol) of sodium chloroacetate for alkoxylated monoamines or488 g (3.6 mol) of sodium chloroacetate for alkoxylated diamines werethen introduced and the reaction mixture was heated to 50° C. After ineach case 30 min, 192 g (4.8 mol) or 144 g (3.6 mol) of NaOH microporeswere added in 6 portions in such a way that the temperature did notexceed 55° C. Reaction was continued at 70° C. for 2 h. Afterwards, 10%hydrochloric acid was metered in until a pH of <3 had been attained. Themixture was then heated to 95° C. and transferred to a heatable stirredapparatus having a bottom outlet. The phases were separated after 15 minat 105-108° C. The aqueous lower phase was discarded. In the case ofproducts which cannot be separated by heating above the cloud point, thewater of reaction was removed distillatively and the salt whichprecipitated out was filtered off.

Example 1 (Cyclopentylamine+2 EO-ECA)

[0074] 370 g of cyclopentylamine+2 EO (OH number: 606.0 mg KOH/g) wereused to obtain 600 g of cyclopentylamine+2 EO-ECA having AN=354.2 mgKOH/g (yield 95.0% conversion) and basic N=4.84%.

Example 2 (Cyclopentylamine+6 EO-ECA)

[0075] 745 g of cyclopentylamine+6 EO (OH number: 301.1 mg KOH/g) wereused to obtain 1017 g of cyclopentylamine+6 EO-ECA having AN=212.4 mgKOH/g (corresponding to 92.5% conversion) and basic N=2.84%.

Example 3 (Cyclohexylamine+2 EO-ECA)

[0076] 398 g of cyclohexylamine+2 EO (OH number: 564.0 mg KOH/g) wereused to obtain 627 g of cyclohexylamine+2 EO-ECA having AN=341.6 mgKOH/g (corresponding to 95.9% conversion) and basic N=4.50%.

Example 4 (Cyclohexylamine+6 EO-ECA)

[0077] 725 g of cyclopentylamine+6 EO (OH number: 309.6 mg KOH/g) wereused to obtain 975 g of cyclopentylamine+6 EO-ECA having AN=220.3 mgKOH/g (corresponding to 93.9% conversion) and basic N=2.89%.

Example 5 (n-butylamine+2 EO-ECA)

[0078] 346 g of n-butylamine+2 EO (OH number: 648.7 mg KOH/g) were usedto obtain 579 g of n-butylamine+2 EO-ECA having AN=377.1 mg KOH/g(corresponding to 97.1% conversion) and basic N=4.62%.

Example 6 (n-butylamine+6 EO-ECA)

[0079] 699 g of n-butylamine+6 EO (OH number: 321.1 mg KOH/g) were usedto obtain 970 g of n-butylamine+6 EO-ECA having AN=221.5 mg KOH/g(corresponding to 91.9% conversion) and basic N=3.00%.

Example 7 (n-butylamine+10 EO-ECA)

[0080] 1032 g of n-butylamine+10 EO (OH number: 217.5 mg KOH/g) wereused to obtain 1320 g of n-butylamine+10 EO-ECA having AN=148.7 mg KOH/g(corresponding to 83.7% conversion) and basic N=1.89%.

Example 8 (Isobutylamine+6 EO-ECA)

[0081] 722 g of isobutylamine+6 EO (OH number: 310.9 mg KOH/g) were usedto obtain 995 g of isobutylamine+6 EO-ECA having AN=219.2 mg KOH/g(corresponding to 93.2% conversion) and basic N=3.01%.

Example 9 (Isobutylamine+10 EO-ECA)

[0082] 1120 g of isobutylamine+10 EO (OH number: 200.4 mg KOH/g) wereused to obtain 1384 g of isobutylamine+10 EO-ECA having AN=135.6 mgKOH/g (corresponding to 91.6% conversion) and basic N=2.08%.

Example 10 (Caprylamine+6 EO-ECA)

[0083] 801 g of caprylamine+6 EO (OH number: 280.1 mg KOH/g) were usedto obtain 1045 g of caprylamine+6 EO-ECA having AN=200.9 mg KOH/g(corresponding to 92.5% conversion) and basic N=2.69%.

Example 11 (Caprylamine+10 EO-ECA)

[0084] 1147 g of caprylamine+10 EO (OH number: 195.7 mg KOH/g) were usedto obtain 1412 g of caprylamine+10 EO-ECA having AN=144.9 mg KOH/g(corresponding to 89.0% conversion) and basic N=1.90%.

Example 12 (Tallow Fat Propylenediamine+10 EO-ECA)

[0085] 768 g of tallow fat propylenediamine+10 EO (OH number: 219.2 mgKOH/g) were used to obtain 970 g of tallow fat propylenediamine+10EO-ECA having AN=156.7 mg KOH/g (corresponding to 87.7% conversion) andbasic N=2.88%.

Example 13 (Tallow Fat Propylenediamine+25 EO-ECA)

[0086] 1316 g of tallow fat propylenediamine+25 EO (OH number: 127.9 mgKOH/g) were used to obtain 1700 g of tallow fat propylenediamine+25EO-ECA having AN=85.0 mg KOH/g (corresponding to 84.0% conversion) andbasic N=1.49%.

Example 14 (Tallow Fat Propylenediamine+30 EO-ECA)

[0087] 1699 g of tallow fat propylenediamine+30 EO (OH number: 99.1 mgKOH/g) were used to obtain 2043 g of tallow fat propylenediamine+30EO-ECA having AN=66.5 mg KOH/g (corresponding to 80.9% conversion) andbasic N=1.30%.

Example 15 (Tallow Fat Propylenediamine+35 EO-ECA)

[0088] 1919 g of tallow fat propylenediamine+35 EO (OH number: 87.7 mgKOH/g) were used to obtain 2301 g of tallow fat propylenediamine+35EO-ECA having AN=63.2 mg KOH/g (corresponding to 85.5% conversion) andbasic N=1.19%.

Example 16 (Laurylpropylenediamine+10 EO-ECA)

[0089] 673 g of laurylpropylenediamine+10 EO (OH number: 250.0 mg KOH/g)were used to obtain 1071 g of laurylpropylenediamine+10 EO-ECA havingAN=149.2 mg KOH/g (corresponding to 90.5% conversion) and basic N=2.54%.

Example 17 (Laurylpropylenediamine+30 EO-ECA)

[0090] 1639 g of laurylpropylenediamine+30 EO (OH number: 102.7 mgKOH/g) were used to obtain 1964 g of laurylpropylenediamine+30 EO-ECAhaving AN=82.3 mg KOH/g (corresponding to 97.1% conversion) and basicN=1.40%.

[0091] b) General Method for the Preparation of AlkoxylatedAmine-ethercarboxylic Alkyl Esters

[0092] A stirred apparatus was initially charged with 1 mol or 0.5 mol(according to AN) of the appropriate alkoxylated alkylamine- oralkylenediamine-ethercarboxylic acid with nitrogen purging and admixedwith an excess (approx. 1.5 molar equivalents) of alcohol. Afteraddition of 0.5% by weight of FASCAT 4100 (butylstannic acid), themixture was heated to from 100° C. to 180° C. at which the water ofreaction distilled off. After a reaction time of 8 hours or attainmentof an acid number of AN<5 mg KOH/g, the reaction was ended and excessalcohol and/or residual water were removed distillatively under reducedpressure.

Example 18 (Cyclopentylamine+2 EO-2-ethylhexyl ECA Ester)

[0093] 317 g of cyclopentylamine+2 EO-ECA and 391 g of 2-ethylhexanolwere used to obtain 521 g of cyclopentylamine+2 EO-2-ethylhexyl ECAester having AN=2.8 mg KOH/g and HN=209.3 mg KOH/g (corresponding to98.7% conversion).

Example 19 (Cyclopentylamine+6 EO-2-ethylhexyl ECA Ester)

[0094] 528 g of cyclopentylamine+6 EO-ECA and 391 g of 2-ethylhexanolwere used to obtain 705 g of cyclopentylamine+6 EO-2-ethylhexyl ECAester having AN=4.9 mg KOH/g and HN=154.1 mg KOH/g (corresponding to96.8% conversion).

Example 20 (Cyclohexylamine+2 EO-2-ethylhexyl ECA Ester)

[0095] 329 g of cyclohexylamine+2 EO-ECA and 391 g of 2-ethylhexanolwere used to obtain 536 g of cyclohexylamine+2 EO-2-ethylhexyl ECA esterhaving AN=1.8 mg KOH/g and HN=207.2 mg KOH/g (corresponding to 99.1%conversion).

Example 21 (Cyclohexylamine+6 EO-2-ethylhexyl ECA Ester)

[0096] 509 g of cyclopentylamine+6 EO-ECA and 391 g of 2-ethylhexanolwere used to obtain 699 g of cyclopentylamine+6 EO-2-ethylhexyl ECAester having AN=3.3 mg KOH/g and HN=153.4 mg KOH/g (corresponding to97.8% conversion).

Example 22 (n-butylamine+2 EO-2-ethylhexyl ECA Ester)

[0097] 298 g of n-butylamine+2 EO-ECA and 391 g of 2-ethylhexanol wereused to obtain 503 g of n-butylamine+2 EO-2-ethylhexyl ECA ester havingAN=2.4 mg KOH/g and HN=219.5 mg KOH/g (corresponding to 98.9%conversion).

Example 23 (n-butylamine+6 EO-2-ethylhexyl ECA Ester)

[0098] 507 g of n-butylamine+6 EO-ECA and 391 g of 2-ethylhexanol wereused to obtain 707 g of n-butylamine+6 EO-2-ethylhexyl ECA ester havingAN=4.1 mg KOH/g and HN=158.1 mg KOH/g (corresponding to 97.4%conversion).

Example 24 (n-butylamine+10 EO-dodecyl ECA Ester)

[0099] 1032 g of n-butylamine+10 EO-ECA and 559 g of lauryl alcohol wereused to obtain 1320 g of n-butylamine+10 EO-dodecyl ECA ester havingAN=8.7 mg KOH/g and HN=124.3 mg KOH/g (corresponding to 92.9%conversion).

Example 25 (Isobutylamine+6 EO-2-ethylhexyl ECA Ester)

[0100] 512 g of isobutylamine+6 EO-ECA and 391 g of 2-ethylhexanol wereused to obtain 683 g of isobutylamine+6 EO-2-ethylhexyl ECA ester havingAN=5.1 mg KOH/g and HN=152.3 mg KOH/g (corresponding to 96.7%conversion).

Example 26 (Isobutylamine+10 EO-dodecyl ECA Ester)

[0101] 1120 g of isobutylamine+10 EO-ECA and 559 g of lauryl alcoholwere used to obtain 1384 g of isobutylamine+10 EO-dodecyl ECA esterhaving AN=5.6 mg KOH/g and HN=115.4 mg KOH/g (corresponding to 95.2%conversion).

Example 27 (Caprylamine+6 EO-2-ethylhexyl ECA Ester)

[0102] 559 g of caprylamine+6 EO-ECA and 391 g of 2-ethylhexanol wereused to obtain 738 g of caprylamine+6 EO-2-ethylhexyl ECA ester havingAN=3.3 mg KOH/g and HN=147.0 mg KOH/g (corresponding to 97.8%conversion).

Example 28 (Caprylamine+10 EO-2-ethylhexyl ECA Ester)

[0103] 774 g of caprylamine+10 EO-ECA and 391 g of 2-ethylhexanol wereused to obtain 999 g of caprylamine+10 EO-2-ethylhexyl ECA ester havingAN=4.8 mg KOH/g and HN=114.1 mg KOH/g (corresponding to 95.8%conversion).

Example 29 (Tallow Fat Propylenediamine+10 EO-2-ethylhexyl ECA Ester)

[0104] 537 g of tallow fat propylenediamine+10 EO-ECA and 293 g of2-ethylhexanol were used to obtain 688 g of tallow fatpropylenediamine+10 EO-2-ethylhexyl ECA ester having AN=4.7 mg KOH/g andHN=121.3 mg KOH/g (corresponding to 96.1% conversion).

Example 30 (Tallow Fat Propylenediamine+25 EO-ethylhexyl ECA Ester)

[0105] 990 g of tallow fat propylenediamine+25 EO-ECA and 293 g of2-ethylhexanol were used to obtain 1068 g of tallow fatpropylenediamine+25 EO-2-ethylhexyl ECA ester having AN=6.7 mg KOH/g andHN=74.6 mg KOH/g (corresponding to 91.0% conversion).

Example 31 (Tallow Fat Propylenediamine+30 EO-ethylhexyl ECA Ester)

[0106] 1266 g of tallow fat propylenediamine+30 EO-ECA and 293 g of2-ethylhexanol were used to obtain 1374 g of tallow fatpropylenediamine+30 EO-2-ethylhexyl ECA ester having AN=3.5 mg KOH/g andHN=61.7 mg KOH/g (corresponding to 94.3% conversion).

Example 32 (Tallow Fat Propylenediamine+35 EO-dodecyl ECA Ester)

[0107] 1332 g of tallow fat propylenediamine+35 EO-ECA and 419 g oflauryl alcohol were used to obtain 1523 g of tallow fatpropylenediamine+35 EO2-dodecyl ECA ester having AN=4.9 mg KOH/g andHN=54.2 mg KOH/g (corresponding to 90.9% conversion).

Example 33 (Laurylpropylenediamine+10 EO-2-ethylhexyl ECA Ester)

[0108] 564 g of laurylpropylenediamine+10 EO-ECA and 293 g of2-ethylhexanol were used to obtain 703 g of laurylpropylenediamine+10EO-2-ethylhexyl ECA ester having AN=3.6 mg KOH/g and HN=117.9 mg KOH/g(corresponding to 96.9% conversion).

Example 34 (Laurylpropylenediamine+30 EO-2-dodecyl ECA Ester)

[0109] 1023 g of laurylpropylenediamine+30 EO-ECA and 419 g of laurylalcohol were used to obtain 1213 g of laurylpropylenediamine+30EO-2-dodecyl ECA ester having AN=6.0 mg KOH/g and HN=66.8 mg KOH/g(corresponding to 91.0% conversion).

[0110] c) General Method for the Preparation of AlkoxylatedAmine-carboxylic Esters by Reacting with Carboxylic Acids

[0111] A stirred apparatus was initially charged with 1 mol or 0.5 mol(according to OH number) of the appropriate alkoxylated alkylamine oralkylenediamine with nitrogen purging and admixed with 1 molarequivalent of the appropriate carboxylic acid. After addition of 0.5% byweight of FASCAT 4100 (butylstannic acid), the mixture was heated tofrom 100° C. to 200° C., at which the water of reaction distilled off.After a reaction time of 8 hours or the attainment of an acid number ofAN<10 mg KOH/g, the reaction was ended and the residual water removeddistillatively under reduced pressure.

[0112] d) General Method for the Preparation of AlkoxylatedAmine-carboxylic Esters by Reacting with Carboxylic Anhydrides

[0113] A stirred apparatus was initially charged with 1 mol or 0.5 mol(according to OH number) of the appropriate alkoxylated alkylamine oralkylenediamine with nitrogen purging and admixed with 1 molarequivalent of the appropriate carboxylic anhydride. The mixture washeated to from 100° C. to 150° C. After a reaction time of 8 h at thisreaction temperature, the carboxylic acid released was distilled off.

Example 35 (n-butylamine+2 EO Acetic Ester)

[0114] 173 g of n-butylamine+2 EO (OH number: 648.7 mg KOH/g) and 204 gof acetic anhydride were used to obtain 262 g of n-butylamine+2 EOacetic ester having AN=0.4 mg KOH/g and HN=440.7 mg KOH/g.

Example 36 (n-butylamine+6 EO Acetic Ester)

[0115] 349 g of n-butylamine+6 EO (OH number: 321.1 mg KOH/g) and 204 gof acetic anhydride were used to obtain 434 g of n-butylamine+6 EOacetic ester having AN=0.1 mg KOH/g and HN=260.2 mg KOH/g.

Example 37 (n-butylamine+6 EO Propionic Ester)

[0116] 349 g of n-butylamine+6 EO (OH number: 321.1 mg KOH/g) and 260 gof propionic anhydride were used to obtain 465 g of n-butylamine+6 EOpropionic ester having AN=0.7 mg KOH/g and HN=244.9 mg KOH/g.

Example 38 (n-butylamine+6 EO 2-ethylhexanoic Ester)

[0117] 349 g of n-butylamine+6 EO-ECA (OH number: 321.1 mg KOH/g) and288 g of 2-ethylhexanoic acid were used to obtain 594 g ofn-butylamine+6 EO 2-ethylhexanoic ester having AN=6.4 mg KOH/g andHN=191.8 mg KOH/g.

Example 39 (Caprylamine+6 EO Acetic Ester)

[0118] 401 g of caprylamine+6 EO (OH number: 280.1 mg KOH/g) and 204 gof acetic anhydride were used to obtain 484 g of caprylamine+6 EO aceticester having AN=0.2 mg KOH/g and HN=231.5 mg KOH/g.

Example 40 (Caprylamine+6 EO Propionic Ester)

[0119] 401 g of caprylamine+6 EO (OH number: 280.1 mg KOH/g) and 260 gof propionic anhydride were used to obtain 517 g of caprylamine+6. EOpropionic ester having AN=0.4 mg KOH/g and HN=220.8 mg KOH/g.

Example 41 (Caprylamine+6 EO 2-ethylhexanoic Ester)

[0120] 401 g of caprylamine+6 EO (OH number: 280.1 mg KOH/g) and 288 gof 2-ethylhexanoic acid were used to obtain 643 g of caprylamine+6 EO2ethylhexanoic ester having AN=8.1 mg KOH/g and HN=179.6 mg KOH/g.

Example 42 (Tallow Fat Propylenediamine+25 EO Propionic Ester)

[0121] 658 g of tallow fat propylenediamine+25 EO (OH number: 127.9 mgKOH/g) and 195 g of propionic anhydride were used to obtain 750 g oftallow fat propylenediamine+25 EO propionic ester having AN=0.7 mg KOH/gand HN=114.3 mg KOH/g.

Example 43 (Tallow Fat Propylenediamine+25 EO 2-ethylhexanoic Ester)

[0122] 658 g of tallow fat propylenediamine+25 EO (OH number: 127.9 mgKOH/g) and 216 g of 2-ethylhexanoic acid were used to obtain 859 g oftallow fat propylenediamine+25 EO 2-ethylhexanoic ester having AN=8.6 mgKOH/g and HN=107.6 mg KOH/g.

Example 44 (Tallow Fat Propylenediamine+25 EO Coconut Fatty Acid Ester)

[0123] 658 g of tallow fat propylenediamine+25 EO (OH number: 127.9 mgKOH/g) and 310 g of coconut fatty acid (AN=271.3 mg KOH/g) were used toobtain 951 g of tallow fat propylenediamine+25 EO coconut fatty acidester having AN=4.5 mg OH/g and HN=93.9 mg KOH/g.

Example 45 (Laurylpropylenediamine+30 EO Coconut Fatty Acid Ester)

[0124] 820 g of laurylpropylenediamine+30 EO (OH number: 102.7 mg KOH/g)and 310 g of coconut fatty acid (AN=271.3 mg KOH/g) were used to obtain1107 g of laurylpropylenediamine+30 EO coconut fatty acid ester havingAN=3.6 mg KOH/g and HN=79.9 mg KOH/g.

[0125] e) General Method for the Quaternization of the AlkoxylatedAmine-ethercarboxylic Alkyl Esters or of the AlkoxylatedAmine-carboxylic Esters

[0126] A stirred apparatus was initially charged with 0.5 mol (accordingto HN number) of the appropriate alkoxylated amine-ethercarboxylic alkylester or of the alkoxylated amine-carboxylic ester with nitrogen purgingand heated to 60° C. 0.4 mol of dimethyl sulfate was added dropwisethereto in such a way that the reaction temperature does not exceed80-90° C. The reaction mixture was subsequently stirred at 90° C. for afurther 3 h. This method was used to quaternize the compounds describedby Examples 18 to 45 (Examples 46 to 73, as listed in Table 1).

Example 74

[0127] Polyvinylcaprolactam having MW 5000 g/mol are mixed in a ratio of1:1 with the quat described by Example 51 and terminated inbutyldiglycol.

Example 75

[0128] Polyvinylcaprolactam having MW 5000 g/mol are mixed in a ratio of1:1 with the quat described by Example 66 and terminated inbutyldiglycol.

[0129] Effectiveness of the Compounds According to the Invention as GasHydrate Inhibitors

[0130] To investigate the inhibiting action of the compounds accordingto the invention, a stirred steel autoclave having temperature control,pressure and torque sensor having an internal volume of 450 ml was used.For investigations of kinetic inhibition, the autoclave was filled withdistilled water and gas in a volume ratio of 20:80, and, forinvestigations of agglomerate inhibition, condensate was additionallyadded. Finally, natural gas was injected at different pressures.

[0131] Starting from a starting temperature of 17.5° C., the autoclavewas cooled to 2° C. within 2 h, then stirred at 2° C. for 18 h andheated back up to 17.5° C. within 2 h. An initial pressure decreasecorresponding to the thermal compression of the gas is observed. Whenthe formation of gas hydrate nuclei occurs during the supercooling time,the pressure measured falls, and an increase in the torque measured anda slight increase in temperature can be observed. Without inhibitor,further growth and increasing agglomeration of the hydrate nuclei leadrapidly to a further increase in the torque. When the mixture is heated,the gas hydrates decompose, so that the starting state of theexperimental series is attained.

[0132] The measure used for the inhibiting action of the compoundsaccording to the invention is the time from the attainment of theminimum temperature of 2° C. up to the first gas absorption (T_(ind)) orthe time up to the rise of the torque (T_(agg)). Long induction times oragglomeration times indicate action as a kinetic inhibitor. On the otherhand, the torque measured in the autoclave serves as a parameter for theagglomeration of the hydrate crystals. The pressure drop measured (Δp)allows a direct conclusion on the amount of hydrate crystals formed. Inthe case of a good antiagglomerate, the torque which builds up afterformation of gas hydrates is distinctly reduced compared to the blankvalue. Ideally, the snowlike, fine hydrate crystals form in thecondensate phase and do not agglomerate and thus do not lead to blockageof the installations serving for gas transport and for gas extraction.

[0133] Test Results

[0134] Composition of the natural gas used:

[0135] Gas 1: 79.3% methane, 10.8% ethane, 4.8% propane, 1.9% butane,1.4% carbon dioxide, 1.8% nitrogen. Supercooling below the equilibriumtemperature of hydrate formation at 50 bar: 12° C.

[0136] Gas 2: 92.1% methane, 3.5% ethane, 0.8% propane, 0.7% butane,0.6% carbon dioxide, 2.3% nitrogen. Supercooling below the equilibriumtemperature of hydrate formation at 50 bar: 7° C., supercooling at 100bar: 12° C.

[0137] In order to test the effectiveness as agglomerate inhibitors, thetest autoclave used above was initially charged with water and whitespirit (20% of the volume in a ratio of 1:2) and, based on the aqueousphase, 5000 ppm of the particular additive were added. At an autoclavepressure of 90 bar using gas 1 and a stirrer speed of 5000 rpm, thetemperature was cooled from initially 17.5° C. within 2 hours to 2° C.,then the mixture was stirred at 2° C. for 25 hours and heated again. Thepressure drop caused by hydrate formation and the resulting torque atthe stirrer, which is a measure of the agglomeration of the gashydrates, were measured. TABLE 1 (Test as antiagglomerant) TemperaturePressure drop rise Torque Example Quat from Δp (bar) ΔT (K) M_(max)(Ncm) Blank — >40 >8 15.9 value 46 Example 18 15.1 0.3 0.3 47 Example 1923.1 2.2 6.3 48 Example 20 15.3 0.7 0.4 49 Example 21 19.9 1.9 5.7 50Example 22 10.1 0.1 0.2 51 Example 23 12.3 0.2 0.2 52 Example 24 16.80.8 0.9 53 Example 25 13.4 0.2 0.3 54 Example 26 10.9 0.2 0.3 55 Example27 17.4 1.9 5.8 56 Example 28 16.6 1.0 0.9 57 Example 29 28.5 3.2 8.8 58Example 30 22.1 2.5 8.3 59 Example 31 15.8 0.8 0.5 60 Example 32 20.62.0 4.9 61 Example 33 16.2 1.1 0.9 62 Example 34 26.8 5.1 9.2 63 Example35 10.3 0.1 0.1 64 Example 36 12.8 0.4 0.5 65 Example 37 11.6 0.4 0.4 66Example 38 9.4 0.0 0.0 67 Example 39 23.0 3.5 2.4 68 Example 40 19.0 2.51.4 69 Example 41 17.0 1.5 1.2 70 Example 42 27.1 5.9 4.8 71 Example 4326.8 5.8 4.4 72 Example 44 14.8 0.8 0.9 73 Example 45 14.5 0.5 1.0Comparison 21.5 1.0 1.5 Comparison 15.0 1.0 1.2

[0138] The comparison substances used were two commercially availableantiagglomerant inhibitors based on tetrabutylammonium bromide.

[0139] As can be seen from these examples, the torques measured weregreatly reduced in comparison to the blank value despite severe hydrateformation. This supports a distinct agglomerate-inhibiting action of theproducts according to the invention. It is obvious that excellentresults are achieved particarly at balanced HL balance.

[0140] In order to test the effectiveness as additives for kineticinhibitors, 5000 ppm of the particular additive, based on the aqueousphase, were added in the test autoclave described above and cooled atdifferent pressures using gases 1 or 2. On attainment of the minimumtemperature of 2° C., the time until the first gas absorption (T_(ind))was recorded. The pressure drop (Δp) measured and the temperature rise ΔT (K) allow the amount of hydrate crystals formed to be concludeddirectly. TABLE 2 (Test as kinetic inhibitors) Tem- Pressure peraturePressure drop rise Example Inhibitor Gas p (bar) T_(ind) Δp (bar) ΔT (K)Blank — 1 50 0 >40 >1.5 value Blank — 2 100 0 >40 >1.5 value 76 Example74 1 50 18.5 h  0 0.0 77 Example 74 2 100 <5 min 6.8 0.2 78 Example 75 150 9.0 h 9.7 0.4 79 Example 75 2 50 6.5 h 11.2 0.3 80 Example 75 2 100  1 h 10.5 0.3 Comparison PVCap 1 50 <5 min 10 0.4 Comparison PVCap 2100 <5 min 6 0.1

[0141] The comparison substance used was a solution ofpolyvinylcaprolactam (PVCap) in butylglycol, molecular weight 5000g/mol.

[0142] As can be recognized from the above test results, the productsaccording to the invention act as a synergistic component of kinetichydrate inhibitors and exhibit a distinct improvement compared to theprior art. They can therefore be used for increasing (synergisticeffect) the performance of prior art inhibitors.

[0143] The corrosion-inhibiting properties of the compounds according tothe invention were demonstrated in the Shell wheel test. Coupons ofcarbon steel (DIN 1.1203 having 15 cm² surface area) were immersed in asalt water/petroleum mixture (9:1.5% NaCl solution, adjusted to pH 3.5using acetic acid) and subjected to this medium at a rotation rate of 40rpm at 70° C. for 24 hours. The dosage of the inhibitor was 50 ppm of a40% solution of the inhibitor. The protection values were calculatedfrom the mass reduction of the coupons, based on a blank value. TABLE 3(SHELL wheel test) Example Corrosion inhibitor % protection Comparison35-40 81 Example 66 86-90 82 Example 69 85-88 83 Example 72 84-90

[0144] The products were also tested in the LPR test (test conditionssimilar to ASTM D 2776). TABLE 4 (LPR test) Protection after [%] ExampleCorrosion inhibitor 10 min 30 min 60 min Comparison 53.9 61.2 73.7 84Example 66 67.7 75.6 79.0 85 Example 69 78.0 85.7 87.9 86 Example 7253.9 67.1 78.6

[0145] The comparison substance used in both tests was a residueamine—quat based on dicocoalkyldimethylammonium chloride (prior artcorrosion inhibitor).

[0146] As can be recognized from the above test results, the inventivegas hydrate inhibitors exhibit corrosion-inhibiting properties and thusconstitute a distinct improvement compared to the prior art. When thecompounds are used as gas hydrate inhibitors, it is therefore possiblein some cases to dispense with additional additization with a corrosioninhibitor. Complicated formulation for the user taking into account thecompatibility of gas hydrate inhibitor and corrosion protectioncomponent can become unnecessary.

What is claimed is:
 1. The use of compounds of the formula 1

where R¹, R² are each independently radicals of the formulae—(B)—(O—A)_(n)—O—CO—R⁵  (2) or —(A—O)_(n)—(C)—CO—O—R⁵  (3) R³ is C₁- toC₃₀-alkyl or C₂- to C₃₀-alkenyl, R⁴ is an organic radical whichoptionally contains heteroatoms and has from 1 to 100 carbon atoms, R⁵is C₁- to C₃₀-alkyl or C₂- to C₃₀-alkenyl, n is a number from 1 to 20, Ais a C₂- to C₄-alkylene group, B is a C₁- to C₁₀-alkylene group, C is aC₁- to C₆-alkylene group and X is an anion as gas hydrate inhibitors. 2.The use as claimed in claim 1, where A is an ethylene or propylenegroup.
 3. The use as claimed in claim 1 and/or 2, where B is a C₂- toC₄-alkylene group.
 4. The use as claimed in one or more of claims 1 to3, where C is a C₂- to C₄-alkylene group.
 5. The use as claimed in oneor more of claims 1 to 4, where n is a number in the range from 2 to 6.6. The use as claimed in one or more of claims 1 to 5, where R⁵ is analkyl or alkenyl group having from 2 to 24 carbon atoms.
 7. The use asclaimed in one or more of claims 1 to 6, where R³ is an alkyl or alkenylgroup having from 2 to 12 carbon atoms.
 8. The use as claimed in one ormore of claims 1 to 7, where R⁴ is a radical of the formula (4)

in which R⁶ is a radical of the formulae —(B)—(O—A)_(n)—O—CO—R⁵  (2) or—(A—O)_(n)—(C)—CO—O—R⁵  (3) or C₁- to C₃₀-alkyl or C₂- to C₃₀-alkenyland k is 2 or
 3. 9. The use as claimed in one or more of claims 1 to 8,where compounds of the formulae (5) to (8)

are used.
 10. A compound of the formula (I), although excluding thosecompounds in which R⁴ contains no heteroatom and R¹ and R² are at thesame time as defined in formula (2).